In many industries it is necessary or desirable to measure the torque required to rotate one of two relatively rotatable components relative to the other of said components for various purposes, e.g., for quality control. Thus, for example, in industries involving the manufacture and/or filling of containers having screw-type closures, e.g., flexible or inflatable tubes or bottles used to contain commodities such as toothpastes, shampoos, lotions, adhesives, oils, etc., it is essential that in the course of manufacture the caps be screwed on tight enough so as not to leak, but also not so hard as to make them difficult to unscrew using only hand action. Hence, a simple and reliable means for measuring the torque required to unscrew such caps is desirable. Similarly, precision shaft bearings for (1) aircraft subassemblies, (2) electric and air motors, (3) hydraulic and pneumatic pumps, and (4) magnetic tape and disk drives, for example, are commonly required to have a torque resistance to rotational movement that falls within predetermined limits, and in many cases it is essential that the torque measuring system be able to rapidly and reliably provide a pass/fail indication in lieu of or in addition to an indication or measurement of torque value.
Heretofore, many different types of torque measuring devices and systems have been produced for various applications. There have been relatively simple cap testers, such as the ones disclosed by the following patents: (1) U.S. Pat. No. 4,539,852, issued Sep. 10, 1985 to Jerome H. Feld, (2) U.S. Pat. No. 4,716,772, issued Jan. 5, 1988 to K. B. Bubech et al, and (3) U.S. Pat. No. 4,794,801, issued Jan. 3, 1989 to T. M. Andrews et al. There have been relatively complex cap testers such as shown by (1) U.S. Pat. No. 38366463, issued Feb. 18, 1975 to D. A. Smith et al, (2) U.S. Pat. No. 4,696,144, issued Jul. 29, 1987 to G. E. Bankuty et al, (3) U.S. Pat. No. 4,811,850, issued Mar. 14, 1989 to G. E. Bankuty et al, and (4) U.S. Pat. No. 4,907,700, issued Mar. 13, 1990 to G. E. Bankuty et al.
Still other forms of torque-measuring systems are known to persons skilled in the art. Such different torque-measuring systems range from those that incorporate or use (a) mechanical dial type torque gages and torque sense-slip clutch mechanisms, as shown, for example, by U.S. Pat. Nos. 4,539,852 and 4,716,772, (b) strain gages as shown by U.S. Pat. Nos. 4,023,404 and 4,811,850, (c) torque sensors producing a digital electronic readout as shown by U.S. Pat. No. 4,794,801, and (d) pneumatic torque-sensing gages as disclosed by U.S. Pat. Nos. 3,866,463 and 4,696,144. See also U.S. Pat. No. 3,495,452, issued Feb. 17, 1970 to C. E. Johnson, Jr. et al for "Torque Meter".